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Smells Trigonometric (Posted on 2023-11-12) Difficulty: 2 of 5
x and y are real numbers such that, (4x3-3x)2+(4y3-3y)2=1.

Find the maximum of x+y.

No Solution Yet Submitted by Danish Ahmed Khan    
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Some Thoughts re: based on Wolfram Alpha | Comment 3 of 4 |
(In reply to based on Wolfram Alpha by Charlie)

Indeed (x,y) = (√2/2,√2/2) solves the equation and x+y = √2


But (x,y) = (0.965926, 0.965926) also solves the equation,
and x+y = 1.931852  which is √(2 + √3) 

In Wolfram Alpha if you put in:
(4x^3-3x)^2+(4y^3-3y)^2=1 intersects y=x

The graph shows a circle and 2 "ellipses" (or at least similar to ellipses) one with the long axis along the y=x line and the other along the y=-x line.  The line y=x intersects both the circle which gives one result and both ellipses which gives the larger result above, as well as a smaller result of (0.258819, 0.258819) which is (√(2 - √3))/2 

  Posted by Larry on 2023-11-12 18:32:50
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